Compound which on heating produces paramagnetic acidic gas?

Options

A. `Mg(NO_(3))_(2)`
B. `Fe_(2)(SO_(4))_(3)`
C. `FeCO_(3)`
D. `HgC_(2)O_(4)`

Explanation

To solve the question "Compound which on heating produces paramagnetic acidic gas?", we will analyze each of the given compounds to determine which one meets the criteria of producing a paramagnetic and acidic gas upon heating.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds given are:
- A) Mg(NO3)2
- B) Fe2(SO4)3
- C) FeCO3
- D) HgC2O4

2. **Analyze Option A: Mg(NO3)2**:
- Upon heating, magnesium nitrate decomposes to form magnesium oxide (MgO), nitrogen dioxide (NO2), and oxygen (O2).
- The reaction can be represented as:
\[ \text{Mg(NO}_3\text{)}_2 \rightarrow \text{MgO} + 2\text{NO}_2 + \text{O}_2 \]
- **Count the Electrons**:
- NO2 has 17 valence electrons (odd number) and is paramagnetic.
- O2 has 12 valence electrons (even number) and is also paramagnetic.
- **Conclusion**: NO2 is an acidic gas and is paramagnetic.

3. **Analyze Option B: Fe2(SO4)3**:
- Upon heating, iron(III) sulfate decomposes to form iron(III) oxide (Fe2O3) and sulfur trioxide (SO3).
- The reaction can be represented as:
\[ \text{Fe}_2(\text{SO}_4)_3 \rightarrow \text{Fe}_2\text{O}_3 + 3\text{SO}_3 \]
- **Count the Electrons**:
- SO3 has 24 valence electrons (even number) and is diamagnetic.
- **Conclusion**: SO3 is an acidic gas but not paramagnetic.

4. **Analyze Option C: FeCO3**:
- Upon heating, iron(II) carbonate decomposes to form iron(II) oxide (FeO), carbon dioxide (CO2), and carbon monoxide (CO).
- The reaction can be represented as:
\[ \text{FeCO}_3 \rightarrow \text{FeO} + \text{CO}_2 + \text{CO} \]
- **Count the Electrons**:
- CO2 has 16 valence electrons (even number) and is diamagnetic.
- CO has 10 valence electrons (even number) and is also diamagnetic.
- **Conclusion**: Both gases are acidic but not paramagnetic.

5. **Analyze Option D: HgC2O4**:
- Upon heating, mercuric oxalate decomposes to form mercury (Hg) and carbon dioxide (CO2).
- The reaction can be represented as:
\[ \text{HgC}_2\text{O}_4 \rightarrow \text{Hg} + 2\text{CO}_2 \]
- **Count the Electrons**:
- CO2 has 16 valence electrons (even number) and is diamagnetic.
- **Conclusion**: CO2 is acidic but not paramagnetic.

6. **Final Conclusion**:
- The only compound that produces a paramagnetic acidic gas upon heating is **Mg(NO3)2**, as it produces NO2, which is paramagnetic and acidic.

### Final Answer:
**The compound which on heating produces a paramagnetic acidic gas is Mg(NO3)2.**